Effect of the nature of the metal on the breathing steps in MOFs with dynamic frameworks.

The thermal behaviour of the nanoporous iron(iii) terephthalate MIL-53 is in stark contrast to its chromium and aluminium analogues which show an expansion of the cell during dehydration; with iron, reversible dehydration occurs via evolution of the structure through a highly distorted metastable anhydrous phase to a more regular phase above 423 K in which pore volume remains approximately constant.